The population biology of Charophytes in the context of shallow lake restoration
The charophytes comprise a group of green algae that is now recognised both for its
evolutionary and ecological significance. Ecologically, the larger charophytes (charales)
are important colonizers of the bottom sediments of lakes and slowly flowing rivers,
where they can form dense monocultures or communities with a variety of submerged
angiosperm species ('macrophytes'),but population changes in these plants are often
difficult to predict
High sediment shear strengths are associated with greater abundance of charophytes.
Distribution of 00 spores through water movement is unlikely. Charophyte oospores will
sink below the depth at which they are capable of emergence in sediments with very low
Oospores will not germination in anoxic conditions, but oospores of Chara vulgaris will
achieve germination in most other conditions. A method of showing viability in
charophyte oospores, which eliminates the need for extensive germination trials is
Chara intermedia grows better at low light flux densities, but will not outcompete other
macrophytes Re-growth from small fragments of charophyte stem is possible in
sediments with low shear strength. These fragments respond to a range of planting
methods, but this achievement is difficult to duplicate under field conditions.
Charophyte growth rates are particularly sensitive to water temperature, and the process
of gametangia formation depends on raised water temperatures. A model suggesting the
charophyte population response to water temperatures, and length of growing season is
presented. The actual response of charophyte populations to temperature fluctuations
over a period of 18 years is examined.
Antifouling paints contain substances that cause stress to charophytes. They also contain
high concentrations of copper, enabling the use of sediment total copper content as an
indicator of their past presence. Low biocide concentrations are shown to effect
charophyte growth rates at typical spring temperatures, a time when competition with
other macrophytes is particularly important.